Multilayer reflective film formed substrate, reflective mask blank, mask blank, methods of manufacturing the same, reflective mask, and mask

ABSTRACT

Provided is a multilayer reflective film formed substrate formed with a fiducial mark for accurately managing coordinates of defects. A multilayer reflective film formed substrate is formed with a multilayer reflective film, which is adapted to reflect EUV light, on a substrate and a fiducial mark which serves as a reference for a defect position in defect information is formed on the multilayer reflective film. The fiducial mark includes a main mark for determining a reference point for the defect position and auxiliary marks arranged around the main mark. The main mark has a point-symmetrical shape and has a portion with a width of 200 nm or more and 10 μm or less with respect to a scanning direction of an electron beam writing apparatus or defect inspection light.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2013/052599 filed Feb. 5, 2013, claiming priority based onJapanese Patent Application Nos. 2012-027638, filed Feb. 10, 2012 and2012-289264, filed Dec. 30, 2012, the contents of all of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

This invention relates to a multilayer reflective film formed substrate,a reflective mask blank, a reflective mask, a mask blank, and a maskwhich are for use in the manufacture of semiconductor devices or thelike, and further to a method of manufacturing the multilayer reflectivefilm formed substrate, a method of manufacturing the reflective maskblank, and a method of manufacturing the mask blank.

BACKGROUND ART

Generally, fine pattern formation is carried out by the photolithographyin manufacturing processes of a semiconductor device. A number oftransfer masks called photomasks are normally used for this fine patternformation. The transfer mask comprises generally a transparent glasssubstrate having thereon a fine pattern made of a metal thin film or thelike. The photolithography is used also in the manufacture of thetransfer mask.

In the manufacture of a transfer mask by the photolithography, use ismade of a mask blank having a thin film (e.g. a light-shielding film orthe like) for forming a transfer pattern (mask pattern) on a transparentsubstrate such as a glass substrate. The manufacture of the transfermask using the mask blank comprises a writing process of writing arequired pattern on a resist film formed on the mask blank, a developingprocess of, after the writing, developing the resist film to form arequired resist pattern, an etching process of etching the thin filmusing this resist pattern as a mask, and a process of stripping andremoving the remaining resist pattern. In the developing process, adeveloper is supplied after writing the required pattern on the resistfilm formed on the mask blank to dissolve a portion of the resist filmsoluble in the developer, thereby forming the resist pattern. In theetching process, using this resist pattern as a mask, an exposed portionof the thin film, where the resist pattern is not formed, is removed bydry etching or wet etching, thereby forming a required mask pattern onthe transparent substrate. In this manner, the transfer mask iscompleted.

As a type of transfer mask, a phase shift mask is known apart from aconventional binary mask having a light-shielding film pattern made of achromium-based material on a transparent substrate. This phase shiftmask is configured to have a phase shift film on a transparentsubstrate. This phase shift film is adapted to provide a predeterminedphase difference and is made of, for example, a material containing amolybdenum silicide compound or the like. Further, use has also beenmade of a binary mask using, as a light-shielding film, a materialcontaining a metal silicide compound such as a molybdenum silicidecompound.

In recent years, with higher integration of semiconductor devices,patterns finer than the transfer limit of the photolithography using theconventional ultraviolet light have been required in the semiconductorindustry. In order to enable formation of such fine patterns, the EUVlithography being an exposure technique using extreme ultraviolet(Extreme Ultra Violet: hereinafter referred to as “EUV”) light isexpected to be promising. Herein, the EUV light represents light in awavelength band of the soft X-ray region or the vacuum ultravioletregion and, specifically, light having a wavelength of about 0.2 to 100nm. A reflective mask has been proposed as a mask for use in the EUVlithography. In the reflective mask, a multilayer reflective film forreflecting exposure light is formed on a substrate and an absorber filmfor absorbing exposure light is formed in a pattern on the multilayerreflective film.

With the increasing demand for miniaturization in the lithographyprocess as described above, problems in the lithography process arebecoming remarkable. One of them is a problem about defect informationof a substrate for a mask blank or the like for use in the lithographyprocess.

Conventionally, taking the center of a substrate as the origin (0,0),the existing position of a defect of the substrate is specified by thedistance from the origin (0,0) in mask blank inspection or the like. Asa consequence, the position accuracy is low and there is variation indetection among apparatuses and thus, when patterning apattern-formation thin film while avoiding the defect at the time ofpattern writing, it is difficult to avoid it on the order of μm.Therefore, the defect is avoided by changing the direction of patterntransfer or roughly shifting the pattern transfer position on the orderof mm.

Under these circumstances, for the purpose of enhancing the inspectionaccuracy of a defect position, there has been a proposal, for example,to form a fiducial mark on a substrate for a mask blank and to specify aposition of a defect using the fiducial mark as a reference position.

Patent Document 1 discloses that, in order to accurately specify aposition of a minute defect having a sphere-equivalent diameter of about30 nm, at least three marks each having a sphere-equivalent diameter of30 to 100 nm are formed on a film-forming surface of a substrate for areflective mask blank for EUV lithography.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: WO2008/129914

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

It is theoretically possible to enhance the inspection accuracy of adefect position of a mask blank by the method disclosed in PatentDocument 1. However, since the size of the mark is as small as 30 to 100nm in terms of sphere-equivalent diameter, there is a problem, forexample, that it is difficult to detect the mark by a usually useddefect inspection apparatus or the like and that the detectionreproducibility is poor, so that a reference position for specifying adefect position is difficult to determine. Patent Document 1 disclosesforming auxiliary marks around the mark for identifying this mark.However, even if the position where the mark is formed can be roughlyspecified using these auxiliary marks, the presence of the mark itselfcannot be easily recognized without using a special inspection apparatuswith extremely high detection accuracy and thus it is difficult tospecify an exact reference point.

Recently, there has been proposed an attempt to correct writing databased on defect data of a mask blank and device pattern data so that anabsorber pattern is formed at a portion where a defect is present,thereby carrying out defect mitigation (Defect mitigation technology).In order to achieve this technology, a fiducial mark is detected also byan electron beam of an electron beam writing apparatus in a state of aresist film formed mask blank in which an absorber film is formed on amultilayer reflective film and further a resist film for forming anabsorber pattern is formed, and then, based on a detected referencepoint, electron beam writing is carried out according tocorrected/modified writing data. Thus, a certain contrast is requiredfor electron beam scanning with respect also to the fiducial mark. Inthe case of the mark with the size disclosed in Patent Document 1, thereis a problem that the contrast for electron beam scanning cannot besufficiently obtained.

In order to form a fiducial mark on a substrate for a mask blank or thelike and to manage (coordinately manage) relative positions between thisfiducial mark and a defect with high accuracy, it is required that thefiducial mark be easily detected, i.e. be surely detected, and furtherthat variation in defect detection position based on the fiducial markbe small (e.g. in order to achieve the Defect mitigation technologydescribed above, variation in defect detection position when thefiducial mark is used as a reference point should be 100 nm or less).However, the conventional technique disclosed in Patent Document 1 orthe like is still insufficient for satisfying such a requirement.

Therefore, this invention has been made in view of such conventionalproblems and its object is, first, to provide a multilayer reflectivefilm formed substrate, a reflective mask blank, and a mask blank eachformed with a fiducial mark for accurately managing coordinates of adefect, second, to provide a reflective mask and a mask each using themask blank or the like and reduced in defects, and, third, to provide amultilayer reflective film formed substrate manufacturing method, areflective mask blank manufacturing method, and a mask blankmanufacturing method, which each correlate a multilayer reflective filmformed substrate, a reflective mask blank, or a mask blank having afiducial mark which is formed on an edge basis or having a fiducial markwhich is formed and then a formation position of which is specified by acoordinate measuring apparatus and formation position information of thefiducial mark with each other.

Means for Solving the Problem

In order to solve the above-mentioned problems, the present inventorshave paid attention particularly to the size and shape of a fiducialmark and, as a result of intensive studies, have found that if afiducial mark comprising a main mark having a point-symmetrical shapeand a size in a specific range and auxiliary marks arranged around themain mark is formed, it is possible to surely detect the fiducial markby either an electron beam writing apparatus or an optical defectinspection apparatus regardless of the apparatus and further the offsetof a reference point for a defect position, which is determined byscanning with an electron beam or defect inspection light, can be madesmall so that variation in defect detection position inspected based onthe fiducial mark can be suppressed to 100 nm or less. Further, thepresent inventors have also found that if a fiducial mark is formed onan edge basis or if a fiducial mark is formed at an arbitrary positionand then a formation position of the fiducial mark is specified by acoordinate measuring apparatus, the size of the fiducial mark can bemade smaller and, in that case, the fiducial mark may consist of only amain mark.

As a result of further intensive studies based on the elucidated factdescribed above, the present inventors have completed this invention.

Specifically, in order to solve the above-mentioned problems, thisinvention has the following structures.

(Structure 1)

A multilayer reflective film formed substrate, comprising a substrate; amultilayer reflective film which is formed on the substrate and whichreflects EUV light; and a fiducial mark which serves as a reference fora defect position in defect information; wherein the fiducial markcomprises a main mark for determining a reference point for the defectposition, and wherein the main mark has a point-symmetrical shape andhas a portion with a width of 200 nm or more and 10 μm or less withrespect to a scanning direction of an electron beam or defect inspectionlight.

As recited in Structure 1, the multilayer reflective film formedsubstrate according to this invention is formed with the fiducial markwhich serves as the reference for the defect position in the defectinformation and this fiducial mark comprises the main mark fordetermining the reference point for the defect position. This main markhas the point-symmetrical shape and has the portion with the width of200 nm or more and 10 μm or less with respect to the scanning directionof the electron beam or the defect inspection light. The fiducial markthus configured can be easily detected, i.e. can be surely detected, byeither an electron beam writing apparatus or an optical, EUV light, orelectron beam defect inspection apparatus. Further, since the main markhas the point-symmetrical shape, the offset of the reference point,which is determined by scanning with the electron beam or the defectinspection light, can be made small. If the fiducial mark is formed onan edge basis or if the fiducial mark is formed at an arbitrary positionand then a formation position of the fiducial mark is specified by acoordinate measuring apparatus, the size of the fiducial mark can bemade smaller and, in that case, the fiducial mark may consist of onlythe main mark. When the size of the fiducial mark can be reduced asdescribed above, if, for example, FIB (focused ion beam) is used as afiducial mark forming means, the processing time can be shortened, andfurther, the fiducial mark detection time can also be shortened.Therefore, variation in defect detection position inspected based on thefiducial mark is small. By this, in defect inspection, it is possible todetermine a reference point for a defect position and to obtain accuratedefect information (defect map) including defect position (relativepositions between the reference point and a defect) information.Further, in the manufacture of a mask, it is possible to collatepre-designed writing data (mask pattern data) with this defectinformation and to accurately correct (modify) the writing data so as toreduce the influence due to defects and, as a result, it is possible toreduce defects in a finally manufactured reflective mask.

(Structure 2)

A multilayer reflective film formed substrate, comprising a substrate; amultilayer reflective film which is formed on the substrate and whichreflects EUV light; and a fiducial mark which serves as a reference fora defect position in defect information; wherein the fiducial markcomprises a main mark for determining a reference point for the defectposition and an auxiliary mark arranged around the main mark, andwherein the main mark has a point-symmetrical shape and has a portionwith a width of 200 nm or more and 10 μm or less with respect to ascanning direction of an electron beam or defect inspection light.

As recited in Structure 2, the multilayer reflective film formedsubstrate according to this invention is formed with the fiducial markwhich serves as the reference for the defect position in the defectinformation and this fiducial mark comprises the main mark fordetermining the reference point for the defect position and theauxiliary mark arranged around the main mark. This main mark has thepoint-symmetrical shape and has the portion with the width of 200 nm ormore and 10 μm or less with respect to the scanning direction of theelectron beam or the defect inspection light. The fiducial mark thusconfigured can be easily detected, i.e. can be surely detected, byeither an electron beam writing apparatus or an optical defectinspection apparatus. Further, since the main mark has thepoint-symmetrical shape, the offset of the reference point, which isdetermined by scanning with the electron beam or the defect inspectionlight, can be made small. Therefore, variation in defect detectionposition inspected based on the fiducial mark is small. By this, indefect inspection, it is possible to determine a reference point for adefect position and to obtain accurate defect information (defect map)including defect position (relative positions between the referencepoint and a defect) information. Further, in the manufacture of a mask,it is possible to collate pre-designed writing data (mask pattern data)with this defect information and to accurately correct (modify) thewriting data so as to reduce the influence due to defects and, as aresult, it is possible to reduce defects in a finally manufacturedreflective mask.

(Structure 3)

The multilayer reflective film formed substrate according to Structure 1or 2, wherein the main mark has a polygonal shape having at least twopairs of sides each perpendicular to and parallel to scanning directionsof the electron beam or the defect inspection light.

As recited in Structure 3, since the main mark has the polygonal shape(e.g. square shape, octagonal shape, or the like) having at least twopairs of sides each perpendicular to and parallel to the scanningdirections of the electron beam writing apparatus or the defectinspection light, it is possible to improve ease (reliability) ofdetection by the electron beam writing apparatus or the defectinspection apparatus and to further suppress variation in defectdetection position.

(Structure 4)

The multilayer reflective film formed substrate according to any ofStructures 1 to 3, wherein the auxiliary mark has a rectangular shapewith long sides perpendicular to and short sides parallel to thescanning direction of the electron beam or the defect inspection light.

As recited in Structure 4, since the auxiliary mark has the rectangularshape with the long sides perpendicular to and the short sides parallelto the scanning direction of the electron beam or the defect inspectionlight, it can be surely detected by scanning with the electron beamwriting apparatus or the defect inspection apparatus so that a positionof the main mark can be easily specified.

(Structure 5)

The multilayer reflective film formed substrate according to any ofStructures 1 to 4, wherein the multilayer reflective film is formed withthe fiducial mark.

As recited in Structure 5, since the multilayer reflective film of themultilayer reflective film formed substrate is formed with the fiducialmark, the fiducial mark can be easily detected by scanning with theelectron beam or the defect inspection light in defect inspection afterthe formation of the multilayer reflective film. Further, it is alsopossible to recycle (reuse) a glass substrate by stripping and removingthe multilayer reflective film without discarding the multilayerreflective film formed substrate in which a defect which cannot beavoided even by correction/modification of writing data or the like isdiscovered in the multilayer reflective film.

(Structure 6)

A reflective mask blank, wherein an absorber film for absorbing the EUVlight is formed on the multilayer reflective film of the multilayerreflective film formed substrate according to any of Structures 1 to 5.

Since the absorber film to be a transfer pattern, which is adapted toabsorb the EUV light, is formed on the multilayer reflective film of themultilayer reflective film formed substrate with the above-mentionedstructure, there is obtained the reflective mask blank formed with thefiducial mark which serves as the reference for the defect position inthe defect information.

(Structure 7)

A reflective mask blank, comprising a substrate; a multilayer reflectivefilm which formed on the substrate and which reflects EUV light; anabsorber film which is formed on the multilayer reflective film andwhich absorbs the EUV light; and a fiducial mark which serves as areference for a defect position in defect information; wherein thefiducial mark comprises a main mark for determining a reference pointfor the defect position, and wherein the main mark has apoint-symmetrical shape and has a portion with a width of 200 nm or moreand 10 μm or less with respect to a scanning direction of an electronbeam or defect inspection light.

As recited in Structure 7, the reflective mask blank according to thisinvention has the absorber film formed with the fiducial mark whichserves as the reference for the defect position in the defectinformation and this fiducial mark comprises the main mark fordetermining the reference point for the defect position. This main markhas the point-symmetrical shape and has the portion with the width of200 nm or more and 10 μm or less with respect to the scanning directionof the electron beam or the defect inspection light. The fiducial markthus configured can be easily detected, i.e. can be surely detected, byeither an electron beam writing apparatus or an optical, EUV light, orelectron beam defect inspection apparatus. Further, since the main markhas the point-symmetrical shape, the offset of the reference point,which is determined by scanning with the electron beam or the defectinspection light, can be made small. If the fiducial mark is formed onan edge basis or if the fiducial mark is formed at an arbitrary positionand then a formation position of the fiducial mark is specified by acoordinate measuring apparatus, the size of the fiducial mark can bemade smaller and, in that case, the fiducial mark may consist of onlythe main mark. When the size of the fiducial mark can be reduced asdescribed above, if, for example, FIB (focused ion beam) is used as afiducial mark forming means, the processing time can be shortened, andfurther, the fiducial mark detection time can also be shortened.Therefore, variation in defect detection position inspected based on thefiducial mark is small. By this, in defect inspection, it is possible todetermine a reference point for a defect position and to obtain accuratedefect information (defect map) including defect position (relativepositions between the reference point and a defect) information.Further, in the manufacture of a mask, it is possible to collatepre-designed writing data (mask pattern data) with this defectinformation and to accurately correct (modify) the writing data so as toreduce the influence due to defects and, as a result, it is possible toreduce defects in a finally manufactured reflective mask.

(Structure 8)

The reflective mask blank according to Structure 7, wherein the absorberfilm is formed with the fiducial mark.

Structure 8 provides advantages such that the risk of occurrence ofdefects on the multilayer reflective film is small in a process offorming the fiducial mark on the absorber film, that since the absorberfilm is made of a material which is processed into an absorber filmpattern when manufacturing a reflective mask, it is easily processed byFIB or etching, and that since the thickness of the absorber film isthin compared to that of the multilayer reflective film, the processingtime can be shortened, which is thus preferable.

(Structure 9)

The reflective mask blank according to Structure 7 or 8, wherein thefiducial mark comprises the main mark and an auxiliary mark arrangedaround the main mark.

As recited in Structure 9, since the fiducial mark comprises the mainmark and the auxiliary mark arranged around the main mark, the main markcan be easily detected by the electron beam writing apparatus or theoptical, EUV light, or electron beam defect inspection apparatus.

(Structure 10)

The reflective mask blank according to any of Structures 7 to 9, whereinthe main mark has a polygonal shape having at least two pairs of sideseach perpendicular to and parallel to scanning directions of theelectron beam or the defect inspection light.

As recited in Structure 10, since the main mark has the polygonal shape(e.g. square shape, octagonal shape, or the like) having at least twopairs of sides each perpendicular to and parallel to the scanningdirections of the electron beam writing apparatus or the defectinspection light, it is possible to improve ease (reliability) ofdetection by the electron beam writing apparatus or the defectinspection apparatus and to further suppress variation in defectdetection position.

(Structure 11)

The reflective mask blank according to Structure 9, wherein theauxiliary mark has a rectangular shape with long sides perpendicular toand short sides parallel to the scanning direction of the electron beamor the defect inspection light.

As recited in Structure 11, since the auxiliary mark has the rectangularshape with the long sides perpendicular to and the short sides parallelto the scanning direction of the electron beam or the defect inspectionlight, it can be surely detected by scanning with the electron beamwriting apparatus or the defect inspection apparatus so that a positionof the main mark can be easily specified.

(Structure 12)

A reflective mask, wherein the absorber film of the reflective maskblank according to any of Structures 6 to 11 is patterned. Thereflective mask obtained by patterning the absorber film of thereflective mask blank with the above-mentioned structure is reduced indefects by correcting/modifying writing data based on the defectinformation of the multilayer reflective film formed substrate or thereflective mask blank.

(Structure 13)

A mask blank, comprising a substrate; a thin film which is formed on thesubstrate and which becomes a transfer pattern; and a fiducial markwhich serves as a reference for a defect position in defect information;wherein the fiducial mark comprises a main mark for determining areference point for the defect position, and wherein the main mark has apoint-symmetrical shape and has a portion with a width of 200 nm or moreand 10 μm or less with respect to a scanning direction of an electronbeam or defect inspection light.

As recited in Structure 13, the mask blank according to this inventionis, as in Structure 1, formed with the fiducial mark which serves as thereference for the defect position in the defect information and thisfiducial mark comprises the main mark for determining the referencepoint for the defect position. This main mark has the point-symmetricalshape and has the portion with the width of 200 nm or more and 10 μm orless with respect to the scanning direction of the electron beam or thedefect inspection light. The fiducial mark thus configured can be easilydetected, i.e. can be surely detected, by either an electron beamwriting apparatus or an optical, EUV light, or electron beam defectinspection apparatus. Further, since the main mark has thepoint-symmetrical shape, the offset of the reference point for thedefect position, which is determined by scanning with the electron beamor the defect inspection light, can be made small. If the fiducial markis formed on an edge basis or if the fiducial mark is formed at anarbitrary position and then a formation position of the fiducial mark isspecified by a coordinate measuring apparatus, the size of the fiducialmark can be made smaller and, in that case, the fiducial mark mayconsist of only the main mark. When the size of the fiducial mark can bereduced as described above, if, for example, FIB (focused ion beam) isused as a fiducial mark forming means, the processing time can beshortened, and further, the fiducial mark detection time can also beshortened. Therefore, variation in defect detection position inspectedbased on the fiducial mark is small. By this, in defect inspection, itis possible to determine a reference point for a defect position and toobtain accurate defect information (defect map) including defectposition (relative positions between the reference point and a defect)information. Further, in the manufacture of a mask, it is possible tocollate pre-designed writing data (mask pattern data) with this defectinformation and to accurately correct (modify) the writing data so as toreduce the influence due to defects and, as a result, it is possible toreduce defects in a finally manufactured mask.

(Structure 14)

A mask blank, comprising a substrate; a thin film which is formed on thesubstrate and which becomes a transfer pattern; and a fiducial markwhich serves as a reference for a defect position in defect information;wherein the fiducial mark comprises a main mark for determining areference point for the defect position and an auxiliary mark arrangedaround the main mark, and wherein the main mark has a point-symmetricalshape and has a portion with a width of 200 nm or more and 10 μm or lesswith respect to a scanning direction of an electron beam or defectinspection light.

As recited in Structure 14, the mask blank according to this inventionis, as in Structure 2, formed with the fiducial mark which serves as thereference for the defect position in the defect information and thisfiducial mark comprises the main mark for determining the referencepoint for the defect position and the auxiliary mark arranged around themain mark. This main mark has the point-symmetrical shape and has theportion with the width of 200 nm or more and 10 μm or less with respectto the scanning direction of the electron beam or the defect inspectionlight. The fiducial mark thus configured can be easily detected, i.e.can be surely detected, by either an electron beam writing apparatus oran optical defect inspection apparatus. Further, since the main mark hasthe point-symmetrical shape, the offset of the reference point for thedefect position, which is determined by scanning with the electron beamor the defect inspection light, can be made small. Therefore, variationin defect detection position inspected based on the fiducial mark issmall. By this, in defect inspection, it is possible to determine areference point for a defect position and to obtain accurate defectinformation (defect map) including defect position (relative positionsbetween the reference point and a defect) information. Further, in themanufacture of a mask, it is possible to collate pre-designed writingdata (mask pattern data) with this defect information and to accuratelycorrect (modify) the writing data so as to reduce the influence due todefects and, as a result, it is possible to reduce defects in a finallymanufactured mask.

(Structure 15)

A mask, wherein the thin film of the mask blank according to Structure13 or 14 is patterned.

The mask obtained by patterning the thin film of the mask blank with theabove-mentioned structure is reduced in defects by modifying writingdata based on the defect information of the mask blank.

(Structure 16)

A method of manufacturing the multilayer reflective film formedsubstrate according to any of Structures 1 to 5, comprising forming thefiducial mark at a predetermined position from an origin which was setbased on edge coordinates of the substrate; and correlating themultilayer reflective film formed substrate comprising the fiducial markand formation position information of the fiducial mark with each other.

In this manner, if the multilayer reflective film formed substrate ismanufactured by correlating the multilayer reflective film formedsubstrate formed with the fiducial mark at the predetermined positionfrom the origin which was set based on the edge coordinates of thesubstrate and the formation position information of the fiducial markwith each other, a user provided with this multilayer reflective filmformed substrate can surely detect the fiducial mark in a short timeusing this formation position information of the fiducial mark.

(Structure 17)

A method of manufacturing the multilayer reflective film formedsubstrate according to any of Structures 1 to 5, comprising specifying,after forming the fiducial mark, a formation position of the fiducialmark by a coordinate measuring apparatus; and correlating the multilayerreflective film formed substrate comprising the fiducial mark andformation position information of the fiducial mark with each other.

In this manner, if the multilayer reflective film formed substrate ismanufactured by specifying, after forming the fiducial mark, theformation position of the fiducial mark by the coordinate measuringapparatus and correlating the multilayer reflective film formedsubstrate formed with the fiducial mark and the formation positioninformation of the fiducial mark with each other, a user provided withthis multilayer reflective film formed substrate can surely detect thefiducial mark in a short time using this formation position informationof the fiducial mark. Since the formation position of the fiducial markis specified by the coordinate measuring apparatus, conversion ofreference coordinates of an electron beam writing apparatus is enabled.Therefore, the user provided with the multilayer reflective film formedsubstrate can accurately collate defect positions easily specified basedon the fiducial mark by a defect inspection apparatus and writing datawith each other so that it is possible to surely reduce defects in afinally manufactured mask.

(Structure 18)

The multilayer reflective film formed substrate manufacturing methodaccording to Structure 16 or 17, further comprising adding defectinformation based on the fiducial mark to the formation positioninformation of the fiducial mark.

As recited in Structure 18, if the multilayer reflective film formedsubstrate is manufactured by adding the defect information based on thefiducial mark to the formation position information of the fiducialmark, the user provided with this multilayer reflective film formedsubstrate can surely detect the fiducial mark in a short time using thisformation position information of the fiducial mark and, in themanufacture of a mask, the user can accurately correct (modify) writingdata based on this defect information so as to reduce the influence dueto defects, thereby reducing defects in a finally manufactured mask.

(Structure 19)

A reflective mask blank manufacturing method, comprising correlating areflective mask blank having an absorber film for absorbing EUV light onthe multilayer reflective film of the multilayer reflective film formedsubstrate comprising the fiducial mark according to any of Structures 16to 18 and the formation position information of the fiducial mark witheach other.

As recited in Structure 19, if the reflective mask blank formed with theabsorber film, which is adapted to absorb the EUV light, on themultilayer reflective film of the multilayer reflective film formedsubstrate formed with the fiducial mark according to any of Structures16 to 18 and the formation position information of the fiducial mark arecorrelated with each other and provided to a user, the user can surelydetect the fiducial mark in a short time using this formation positioninformation of the fiducial mark in the manufacture of a mask using thisreflective mask blank.

(Structure 20)

A method of manufacturing the reflective mask blank according to any ofStructures 6 to 11, comprising forming the fiducial mark at apredetermined position from an origin which was set based on edgecoordinates of the substrate; and correlating the reflective mask blankcomprising the fiducial mark and formation position information of thefiducial mark with each other.

In this manner, if the reflective mask blank is manufactured bycorrelating the reflective mask blank formed with the fiducial mark atthe predetermined position from the origin which was set based on theedge coordinates of the substrate and the formation position coordinatesof the fiducial mark with each other, a user provided with thisreflective mask blank can surely detect the fiducial mark in a shorttime using this formation position information of the fiducial mark.

(Structure 21)

A method of manufacturing the reflective mask blank according to any ofStructures 6 to 11, comprising specifying, after forming the fiducialmark, a formation position of the fiducial mark by a coordinatemeasuring apparatus; and correlating the reflective mask blankcomprising the fiducial mark and formation position information of thefiducial mark with each other.

In this manner, if the reflective mask blank is manufactured byspecifying, after forming the fiducial mark, the formation position ofthe fiducial mark by the coordinate measuring apparatus and correlatingthe reflective mask blank formed with the fiducial mark and theformation position information of the fiducial mark with each other, auser provided with this reflective mask blank can surely detect thefiducial mark in a short time using this formation position informationof the fiducial mark. Since the formation position of the fiducial markis specified by the coordinate measuring apparatus, conversion ofreference coordinates of an electron beam writing apparatus is enabled.Therefore, the user provided with the multilayer reflective film formedsubstrate can accurately collate defect positions easily specified basedon the fiducial mark by a defect inspection apparatus and writing datawith each other so that it is possible to surely reduce defects in afinally manufactured mask.

(Structure 22)

A method of manufacturing the mask blank according to Structure 13 or14, comprising forming the fiducial mark at a predetermined positionfrom an origin which was set based on edge coordinates of the substrate;and correlating the mask blank comprising the fiducial mark andformation position information of the fiducial mark with each other.

As recited in Structure 22, if the mask blank is manufactured bycorrelating the mask blank formed with the fiducial mark at thepredetermined position from the origin which was set based on the edgecoordinates of the substrate and the formation position information ofthe fiducial mark with each other, a user provided with this mask blankcan surely detect the fiducial mark in a short time using this formationposition information of the fiducial mark.

(Structure 23)

A method of manufacturing the mask blank according to Structure 13 or14, comprising specifying, after forming the fiducial mark, a formationposition of the fiducial mark by a coordinate measuring apparatus; andcorrelating the mask blank comprising the fiducial mark and formationposition information of the fiducial mark with each other.

As recited in Structure 23, if the mask blank is manufactured byspecifying, after forming the fiducial mark, the formation position ofthe fiducial mark by the coordinate measuring apparatus and correlatingthe mask blank formed with the fiducial mark and the formation positioninformation of the fiducial mark with each other, a user provided withthis mask blank can surely detect the fiducial mark in a short timeusing this formation position information of the fiducial mark. Sincethe formation position of the fiducial mark is specified by thecoordinate measuring apparatus, conversion of reference coordinates ofan electron beam writing apparatus is enabled. Therefore, the userprovided with the mask blank can accurately collate defect positionseasily specified based on the fiducial mark by a defect inspectionapparatus and writing data with each other so that it is possible tosurely reduce defects in a finally manufactured mask.

(Structure 24)

The mask blank manufacturing method according to Structure 22 or 23,further comprising adding defect information based on the fiducial markto the formation position information of the fiducial mark.

As recited in Structure 24, if the defect information based on thefiducial mark is added to the formation position information of thefiducial mark and provided to the user, the user can surely detect thefiducial mark in a short time using this formation position informationof the fiducial mark and, in the manufacture of a mask, the user canaccurately correct (modify) writing data based on this defectinformation so as to reduce the influence due to defects, therebyreducing defects in a finally manufactured mask.

Effect of the Invention

According to this invention, by forming a fiducial mark that can besurely detected by either an electron beam writing apparatus or a defectinspection apparatus and that allows the offset of a reference point fora defect position, which is determined by scanning with an electron beamor defect inspection light, to be small, it is possible to provide amultilayer reflective film formed substrate, a reflective mask blank,and a mask blank each capable of accurately carrying out management ofcoordinates of a defect (management of relative positions between thefiducial mark and a defect).

Further, according to this invention, it is possible to provide areflective mask and a mask each using the multilayer reflective filmformed substrate or the mask blank and reduced in defects by modifyingwriting data based on defect information thereof.

Further, according to this invention, it is possible to provide amultilayer reflective film formed substrate manufacturing method, areflective mask blank manufacturing method, and a mask blankmanufacturing method, which each correlate a multilayer reflective filmformed substrate, a reflective mask blank, or a mask blank having afiducial mark which is formed on an edge basis or having a fiducial markwhich is formed and then a formation position of which is specified by acoordinate measuring apparatus and formation position information of thefiducial mark with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an example of the arrangement of fiducialmarks in this invention.

FIG. 2 is a diagram showing an example of the shape and arrangement of amain mark and auxiliary marks constituting the fiducial mark in thisinvention.

FIG. 3 is a diagram for explaining a method of determining a referencepoint using the fiducial mark in this invention.

FIG. 4 is diagrams each showing another example of the shape of a mainmark.

FIG. 5 is a diagram showing another example of the shape of auxiliarymarks.

FIG. 6 is a diagram for explaining one example of a method of detectingan auxiliary mark.

FIG. 7 is a cross-sectional view of a multilayer reflective film formedsubstrate according to this invention.

FIG. 8 is a cross-sectional view of a reflective mask blank according tothis invention.

FIG. 9 is a cross-sectional view of a binary mask blank according tothis invention.

FIG. 10 is a cross-sectional view of a reflective mask according to thisinvention.

FIG. 11 is a cross-sectional view of a binary mask according to thisinvention.

FIG. 12 is a photograph showing a cross-sectional shape of a fiducialmark formed in a multilayer reflective film.

FIG. 13 is a diagram showing the relationship between the width of amain mark and the electron beam contrast.

FIG. 14 is a diagram showing the relationship between the width of amain mark and the maximum variation in detection position.

FIG. 15 is a plan view showing another example of the arrangement offiducial marks in this invention.

FIG. 16 is diagrams each showing an example of the shape and arrangementof a fiducial mark when it is formed on an edge basis.

FIG. 17 is a diagram for explaining a method of forming a fiducial markon an edge basis.

FIG. 18 is a diagram for explaining a method of forming a fiducial markon an edge basis.

FIG. 19 is a cross-sectional view of a reflective mask blank accordingto another embodiment of this invention.

MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, embodiments of this invention will be described in detail.

[Fiducial Mark]

First, a fiducial mark in this invention (hereinafter may also bereferred to as a “fiducial mark of this invention”) will be described indetail.

FIG. 1 is a plan view of a mask blank glass substrate showing an exampleof the arrangement of fiducial marks.

In FIG. 1, two kinds of marks, i.e. relatively large rough alignmentmarks 12 and fiducial marks 13 of this invention as relatively smallfine marks, are formed. Although the fiducial marks are shown on asurface of a glass substrate 11 in FIG. 1, FIG. 1 only shows the exampleof the arrangement of the fiducial marks over the main surface of theglass substrate and thus is, of course, not intended to limit thisinvention to the manner in which the fiducial marks are formed directlyon the glass substrate.

The rough alignment mark 12 itself does not have a role of a fiducialmark, but has a role of facilitating detection of a position of thefiducial mark 13. Since the size of the fiducial mark 13 is small, it isdifficult to locate its position by visual observation. On the otherhand, if an attempt is made to detect the fiducial mark 13 usinginspection light or an electron beam from the beginning, the detectiontakes time and, thus, if a resist film is formed, there is a possibilityof causing unwanted resist exposure, which is thus not preferable. Byproviding the rough alignment mark 12 whose positional relationship withthe fiducial mark 13 is determined in advance, the fiducial mark 13 canbe detected quickly and easily.

FIG. 1 shows the example in which the rough alignment marks 12 arearranged at four positions near corners of the main surface of therectangular glass substrate 11 and the fiducial marks 13 are arranged attwo positions near each of the rough alignment marks 12. The roughalignment marks 12 and the fiducial marks 13 are preferably formed on aboundary line of a pattern forming region, defined by a broken line A,of the substrate main surface or on the outer peripheral edge sideoutside the pattern forming region. However, if it is too close to theouter peripheral edge of the substrate, it may be a region where theflatness of the substrate main surface is not good or there is apossibility of crossing another kind of identification mark, which isthus not preferable.

The number of the fiducial marks and the number of the rough alignmentmarks are not particularly limited. With respect to the fiducial marks,the number of them should be at least three and may be three or more.

As will be described hereinbelow, the fiducial mark 13 of this inventioncomprises a main mark for determining a position (reference point) whichserves as a reference for a defect position and auxiliary marks arrangedaround the main mark for roughly specifying the main mark and,therefore, if there is no particular inconvenience in detecting thefiducial mark 13 of this invention with inspection light or an electronbeam from the beginning, it is not necessary to provide the roughalignment mark 12.

That is, in this invention, as shown in FIG. 15, for example, as oneexample, the fiducial marks 13 of this invention may be arranged at fourpositions near the corners of the main surface of the glass substrate 11without providing the above-mentioned rough alignment marks. By this, itis possible to omit the process of forming the relatively large roughalignment marks and thus to significantly shorten the mark processingtime.

FIG. 2 is a diagram showing an example of the shape and arrangement of amain mark and auxiliary marks constituting the fiducial mark of thisinvention. FIG. 3 is a diagram for explaining a method of determining areference point using the fiducial mark of this invention.

The fiducial mark serves as a reference for a defect position in defectinformation. The fiducial mark 13 of this invention comprises a mainmark for determining a position (reference point) which serves as areference for a defect position and auxiliary marks arranged around themain mark. One of features of the fiducial mark of this invention isthat the main mark has a point-symmetrical shape and has a portion witha width of 200 nm or more and 10 μm or less with respect to a scanningdirection of an electron beam or defect inspection light.

FIGS. 2 and 3 show, by way of example, the fiducial mark 13 comprising amain mark 13 a and two auxiliary marks 13 b and 13 c arranged around themain mark 13 a.

In this invention, the main mark 13 a preferably has a polygonal shapehaving at least two pairs of sides each perpendicular to and parallel toscanning directions of an electron beam writing apparatus or defectinspection light (X- and Y-directions in FIG. 3). In this manner, whenthe main mark 13 a has the polygonal shape having at least two pairs ofsides each perpendicular to and parallel to the scanning directions ofthe electron beam or the defect inspection light, it is possible toimprove ease (reliability) of detection by an electron beam writingapparatus or a defect inspection apparatus and to further suppressvariation in defect detection position. FIGS. 2 and 3 show, as aspecific example, a case where the main mark 13 a has a square shapewith the same length in longitudinal and lateral directions (X- andY-directions). In this case, the longitudinal and lateral lengths (L)are each 200 nm or more and 10 μm or less.

The main mark 13 a is satisfactory if it has a point-symmetrical shape.The shape is not limited to the above-mentioned square shape and may be,for example, a square shape with rounded corners as shown at (a) in FIG.4, an octagonal shape as shown at (b) in the same figure, or a crossshape as shown at (c) in the same figure. Also in this case, thedimensions (longitudinal and lateral lengths (L)) of the main mark 13 aare each set to 200 nm or more and 10 μm or less. As a specific example,in the case of the main mark 13 a having the cross shape, its dimensions(longitudinal and lateral lengths) may each be set to 5 μm or more and10 μm or less. Although not illustrated, the main mark 13 a mayalternatively have a perfect circular shape with a diameter of 200 nm ormore and 10 μm or less.

The two auxiliary marks 13 b and 13 c are arranged around the main mark13 a along scanning directions of an electron beam or defect inspectionlight (X- and Y-directions in FIG. 3). In this invention, the auxiliarymarks 13 b and 13 c each preferably have a rectangular shape with longsides perpendicular to and short sides parallel to the scanningdirection of the electron beam or the defect inspection light. When theauxiliary mark has the rectangular shape with the long sidesperpendicular to and the short sides parallel to the scanning directionof the electron beam or the defect inspection light, it can be surelydetected by scanning with the electron beam writing apparatus or thedefect inspection apparatus so that a position of the main mark can beeasily specified. In this case, the long side preferably has a lengthwhich is detectable by the minimum number of times of scanning with theelectron beam writing apparatus or the defect inspection apparatus. Forexample, the long side preferably has a length of 25 μm or more and 600μm or less. On the other hand, if the length of the long side is short,for example, less than 25 μm, there is a possibility that the auxiliarymark cannot be easily detected by scanning with the electron beamwriting apparatus or the defect inspection apparatus. If the length ofthe long side is long, for example, more than 600 μm, the processingtime exceeds one hour per portion depending on a fiducial mark formingmethod, which is thus not preferable. The length of the long side ismore preferably 25 μm or more and 400 μm or less and further preferably25 μm or more and 200 μm or less.

The auxiliary mark 13 b, 13 c and the main mark 13 a may be spaced apartfrom each other by a predetermined distance or are not necessarilyspaced apart from each other. When the auxiliary mark and the main markare spaced apart from each other, the distance therebetween is notparticularly limited, but, in this invention, it is preferably in arange of, for example, about 25 μm to 50 μm.

The main mark 13 a and the auxiliary marks 13 b and 13 c each have aconcave cross-sectional shape and are provided with a required depth ina height direction of the fiducial mark, thereby forming the fiducialmark that can be recognized. In terms of improving the detectionaccuracy by an electron beam or defect inspection light, thecross-sectional shape is preferably formed to widen from the bottom ofthe concave shape toward the surface side and, in this case, theinclination angle of a side wall of the fiducial mark is preferably 75°or more, more preferably 80° or more, and further preferably 85° ormore.

Using the fiducial mark described above, a reference point which servesas a reference for a defect position is determined in the followingmanner (see FIG. 3).

When an electron beam or defect inspection light scans over theauxiliary marks 13 b and 13 c in the X- and Y-directions and detectsthese auxiliary marks, a position of the main mark 13 a can be roughlyspecified. After an electron beam or inspection light scans over themain mark 13 a, whose position was specified, in the X- andY-directions, a reference point is determined as an intersection point P(normally, the approximate center of the main mark) over the main mark13 a (detected by the scanning of the auxiliary marks).

As described above, in this invention, the main mark 13 a has apoint-symmetrical shape and has a portion with a width of 200 nm or moreand 10 μm or less with respect to a scanning direction of an electronbeam or defect inspection light. The present inventors have studied therelationship between the width of the main mark 13 a and the contrastfor an electron beam and the relationship between the width of the mainmark 13 a and the variation in defect detection position. FIG. 13 is adiagram showing the relationship between the main mark width and theelectron beam contrast and FIG. 14 is a diagram showing the relationshipbetween the main mark width and the maximum variation in defectdetection position. FIG. 13 is the diagram showing the relationshipbetween the main mark width and the EB (electron beam) contrast,wherein, with respect to a resist film formed reflective mask blank inwhich, at a predetermined position of a multilayer reflective film(total thickness: 280 nm) which, given that a Si film (thickness: 4.2nm) and a Mo film (thickness: 2.8 nm) formed one cycle, was formed bylaminating Si films and Mo films by 40 cycles on a SiO₂—TiO₂-based glasssubstrate, a square main mark was formed (by removing all layers of themultilayer reflective film by FIB), and a Ru protective film (thickness:2.5 nm), an absorber film (total thickness: 70 nm), and a resist film(thickness: 100 nm) were formed on the multilayer reflective film, theEB reflection intensity which was detected when EB (electron beam)scanned over the main mark was measured. Various sizes of marks wereformed and the electron beam contrast was obtained bycontrast=(Imax−Imin)/(Imax+Imin), where Imin represents an EB (electronbeam) intensity at a bottom portion (glass) of the mark and Imaxrepresents an EB (electron beam) intensity at a multilayer film portion.FIG. 14 shows the results, wherein, with respect to a multilayerreflective film formed substrate in which, at a predetermined positionof a multilayer reflective film (total thickness: 280 nm) which, giventhat a Si film (thickness: 4.2 nm) and a Mo film (thickness: 2.8 nm)formed one cycle, was formed by laminating Si films and Mo films by 40cycles on a SiO₂—TiO₂-based glass substrate, a square main mark wasformed (by removing all layers of the multilayer reflective film byFIB), the main mark was detected and variation in defect detectionposition was measured using a defect inspection apparatus (Teron 600Series manufactured by KLA-Tencor Corporation). Defect inspection wascarried out five times and variation of detected defect positions basedon reference coordinates was obtained as the variation in defectdetection position.

As shown in FIG. 13, the results are such that when the width of themain mark 13 a becomes less than 200 nm, the EB contrast is largelyreduced. That is, since it becomes difficult to detect the main mark byEB (electron beam) scanning, correction/modification of writing datacannot be carried out with high accuracy. The contrast is 0.006 when thewidth of the main mark 13 a is 100 nm while the contrast is 0.016 whenthe width of the main mark 13 a is 200 nm, and therefore, the differencein contrast is 2.75 times. On the other hand, as shown in FIG. 14, whenthe width of the main mark 13 a exceeds 10 μm, variation in defectdetection position exceeds 100 nm. This cannot satisfy the variation indefect detection position of 100 nm or less when the fiducial mark isused as a reference point, which is required for achieving/enabling theabove-mentioned Defect mitigation technology. Therefore, in order tosatisfy both the contrast and the variation in defect detectionposition, it is important that the main mark 13 a have a portion with awidth of 200 nm or more and 10 μm or less with respect to a scanningdirection of an electron beam or defect inspection light.

Further, when, for example, a fiducial mark is formed on a multilayerreflective film and its width is narrow (specifically, when it is 30 to100 nm as described in Patent Document 1), there also occurs aninconvenience that if an absorber film and so on are formed on themultilayer reflective film, a concave portion of the fiducial mark isburied so that it is difficult to detect the fiducial mark.

In the meantime, as described above, the auxiliary marks 13 b and 13 ceach preferably have a rectangular shape with long sides perpendicularto and short sides parallel to a scanning direction of an electron beamor defect inspection light. In this case, the long side preferably has alength which is detectable by the minimum number of times of scanningwith the electron beam writing apparatus or the defect inspectionapparatus, for example, a length of 25 μm or more and 600 μm or less.However, if, for example, this length of about several hundred μm isformed by a focused ion beam, the processing time is required to belong.

In view of this, as shown in FIG. 5, the auxiliary mark can be dividedinto several rectangles. FIG. 6 is an example specifically showing suchan arrangement, wherein rectangular auxiliary marks 13 b 1 to 13 b 6each having a size of 50 μm×1 μm are arranged at regular intervals onone side (Y-direction) of a main mark 13 a having a size of 5 μm×5 μmand the interval (space) between the auxiliary marks is set to 50 μm.

In this case, for example, a first scan (first scanning) misses theauxiliary mark, then a second scan (second scanning) shifted upward(Y-direction) by 60 μm also misses the auxiliary mark, and then a thirdscan (third scanning) shifted further upward by 60 μm can detect theauxiliary mark 13 b 5.

Even if the auxiliary mark is divided and the length of the long side ofeach of the divided individual auxiliary marks is shortened as describedabove, the auxiliary mark can be surely detected with the minimum numberof times of scanning by determining the scanning rule. Further, theoverall processing time can be shortened by dividing the auxiliary markas described above.

The position of forming the main mark 13 a and the auxiliary marks 13 band 13 c which constitute the fiducial mark 13 of this invention is notparticularly limited. For example, in the case of a reflective maskblank, they may be formed at any position as long as it is on afilm-forming surface of a multilayer reflective film. For example, theymay be formed at any position of a substrate, an underlayer (describedlater), a multilayer reflective film, a protective film (capping layer,buffer layer), an absorber film, or an etching mask film formed on theabsorber film.

In the case of a reflective mask which uses EUV light as exposure light,a defect present particularly on a multilayer reflective film is almostimpossible to correct and can be a serious phase defect on a transferpattern and, therefore, defect information on the multilayer reflectivefilm is important in order to reduce transfer pattern defects.Therefore, it is preferable to carry out defect inspection at leastafter forming the multilayer reflective film to obtain defectinformation. For this, it is preferable that a multilayer reflectivefilm formed substrate be formed with a fiducial mark of this invention.In particular, in terms of ease of detection, recycling of a substrate,and so on, it is preferable to form the fiducial mark of this inventionon the multilayer reflective film.

On the other hand, in terms of suppressing a change in opticalproperties (e.g. reflectance) due to cleaning after forming a fiducialmark, it is preferable to form a fiducial mark on an absorber film of areflective mask blank. In this case, since the fiducial mark is notformed at a stage of a multilayer reflective film formed substrate,defect inspection and management of coordinates of defects using thefiducial mark as a reference can be carried out in the following mannerfor the reflective mask blank.

First, with respect to a multilayer reflective film formed substrate inwhich a multilayer reflective film is formed on a substrate, defectinspection is carried out by a defect inspection apparatus using thecenter of a substrate main surface as a reference point, therebyobtaining defects and their position information detected by the defectinspection. Then, a protective film and an absorber film are formed onthe multilayer reflective film and then a fiducial mark of thisinvention is formed at a predetermined position of the absorber film,thereby obtaining a reflective mask blank formed with the fiducial mark.

Defect inspection is carried out by a defect inspection apparatus usingthe fiducial mark as a reference. Since the absorber film is formed overthe multilayer reflective film as described above, defect inspectiondata of this defect inspection also reflects the defect inspection ofthe multilayer reflective film formed substrate obtained above.Therefore, by collating the defect inspection data of the multilayerreflective film formed substrate and the defect inspection data of thereflective mask blank with each other based on those defects which areconsistent between the multilayer reflective film formed substrate andthe reflective mask blank, defect inspection data of the multilayerreflective film formed substrate and defect inspection data of thereflective mask blank, both using the fiducial mark as a reference, canbe obtained.

A method of forming the main mark 13 a and the auxiliary marks 13 b and13 c which constitute the fiducial mark 13 of this invention is notparticularly limited. For example, when the cross-sectional shape of thefiducial mark is concave, the fiducial mark can be formed byphotolithography, recess formation by laser light or an ion beam,machining trace by scanning a diamond stylus, indention by amicro-indenter, stamping by an imprint method, or the like.

As described above, if the fiducial mark of this invention is formed onthe multilayer reflective film formed substrate or the like, thefiducial mark of this invention can be easily detected, i.e. can besurely detected, by either an electron beam writing apparatus or anoptical defect inspection apparatus. Further, since it has thepoint-symmetrical shape, the offset of a reference point for a defectposition, which is determined by scanning with an electron beam ordefect inspection light, can be made small. Therefore, variation indefect detection position inspected based on the fiducial mark is small.By this, in defect inspection, it is possible to determine a referencepoint for a defect position and to obtain accurate defect information(defect map) including defect position (relative positions between thereference point and a defect) information. Further, in the manufactureof a mask, it is possible to collate pre-designed writing data (maskpattern data) with this defect information and to accurately correct(modify) the writing data so as to reduce the influence due to defectsand, as a result, it is possible to reduce defects in a finallymanufactured reflective mask.

In the above-mentioned embodiment, the description has been given of theexample in which the two auxiliary marks 13 b and 13 c are arrangedaround the main mark 13 a along the scanning directions of the electronbeam writing apparatus or the defect inspection apparatus (X- andY-directions). However, this invention is not limited to such anembodiment. For example, in a system where defect detection is not basedon scanning with inspection light, if the positional relationshipbetween a main mark and an auxiliary mark is specified, the arrangementposition of the auxiliary mark relative to the main mark is arbitrary.Further, in this case, not the center of the main mark, but its edge canalternatively be used as a reference point.

In the meantime, as described above, the fiducial mark 13 of thisinvention is formed at an arbitrary position on the boundary line of thepattern forming region, defined by the broken line A, of the substratemain surface or on the outer peripheral edge side outside the patternforming region (see FIGS. 1 and 15). In this case, it is preferable toform the fiducial mark on an edge basis or to specify a fiducial markformation position by a coordinate measuring apparatus after forming thefiducial mark.

First, a method of forming a fiducial mark on the above-mentioned edgebasis will be described. FIGS. 17 and 18 are diagrams each forexplaining a method of forming a fiducial mark on the edge basis.

For example, when forming a fiducial mark on a multilayer reflectivefilm formed substrate using FIB (focused ion beam) as a fiducial markforming means, detection of edges of the multilayer reflective filmformed substrate is carried out. When processing a fiducial mark by FIB,edges of a glass substrate 11 of the multilayer reflective film formedsubstrate can be recognized by a secondary electron image, a secondaryion image, or an optical image. When processing a fiducial mark byanother method (e.g. impression), it can be recognized by an opticalimage. As shown in FIG. 17, for example, edge coordinates of eightportions (circled portions) of four sides of the glass substrate 11(illustration of a multilayer reflective film is omitted forconvenience' sake) are confirmed, and then tilt correction is carriedout to obtain the origin (0,0). The origin in this case can bearbitrarily set and may be a corner or the center of the substrate.

A fiducial mark is formed by FIB at a predetermined position from theorigin which was set on the edge basis as described above. FIG. 18 showsa case where a fiducial mark 13 is formed at a predetermined positionfrom the origin O (0,0) which was set at an arbitrary corner of thesubstrate on an edge basis, specifically, at a position distanced by Xand Y respectively from edges of end faces 11A and 11B both adjacent tothe origin O. In this case, fiducial mark formation coordinates (X,Y)based on the origin O (0,0) serve as fiducial mark formation positioninformation. This also applies to a fiducial mark which is formed atanother position.

When detecting a fiducial mark of a multilayer reflective film formedsubstrate (or a reflective mask blank, a mask blank), formed on such anedge basis, using a defect inspection apparatus or an electron beamwriting apparatus, since fiducial mark formation position information,i.e. distances from edges, is known, it is possible to easily specify aformation position of the fiducial mark.

Alternatively, it is also possible to apply a method of specifying afiducial mark formation position by a coordinate measuring apparatusafter forming a fiducial mark at an arbitrary position of a multilayerreflective film formed substrate. This coordinate measuring apparatusmeasures fiducial mark formation coordinates on an edge basis and usecan be made of, for example, a highly accurate pattern positionmeasuring apparatus (LMS-IPRO4 manufactured by KLA-Tencor Corporation).The specified fiducial mark formation coordinates serve as fiducial markformation position information. The coordinate measuring apparatus alsoserves to carry out conversion into reference coordinates of an electronbeam writing apparatus and, therefore, a user provided with themultilayer reflective film formed substrate can accurately collatedefect positions easily specified based on the fiducial mark by a defectinspection apparatus and writing data with each other so that it ispossible to surely reduce defects in a finally manufactured mask.

As described above, according to the method of forming the fiducial markon the edge basis or specifying the fiducial mark formation position bythe coordinate measuring apparatus after forming the fiducial mark atthe arbitrary position, since it is possible to easily specify theformation position of the fiducial mark of the multilayer reflectivefilm formed substrate or the like using the defect inspection apparatusor the electron beam writing apparatus, it is possible to reduce thesize of the fiducial mark. Specifically, when the fiducial mark 13 ofthis invention comprises the main mark and the auxiliary marks, thewidth of the main mark can be set to 200 nm or more and 10 μm or lessand the length of the long side of the auxiliary mark can be set to, forexample, 25 μm or more and 250 μm or less. When the size of the fiducialmark is reduced as described above, if, for example, the FIB is employedas the fiducial mark forming means, the fiducial mark processing timecan be shortened, which is thus preferable. Further, the fiducial markdetection time can also be shortened, which is thus preferable.

FIG. 16 shows examples of the shape and arrangement of fiducial markswhen forming them on the edge basis as described above, wherein thefiducial mark comprising a main mark 13 a and auxiliary marks 13 b and13 c as shown at (a) in the same figure is a typical example. Since thesize of the fiducial mark can be reduced as described above, theauxiliary marks are not necessarily required and thus, for example, thefiducial mark may consist of only a main mark 13 a as shown at (b) inthe same figure. Alternatively, the fiducial mark may be such that fourauxiliary marks 13 b to 13 e are arranged around a main mark 13 a asshown at (c) in the same figure or the fiducial mark may be across-shaped fiducial mark as shown at (d) in the same figure.

If, for example, a multilayer reflective film formed substrate formedwith a fiducial mark at a predetermined position from the origin whichwas set based on edge coordinates of a substrate and fiducial markformation position information (fiducial mark formation coordinates) inthis case are correlated with each other and provided to a user, theuser can surely detect the fiducial mark in a short time using thisfiducial mark formation position information, for example, in a maskmanufacturing process.

If, for example, after a multilayer reflective film formed substrate isformed with a fiducial mark, a formation position of the fiducial markis specified by a coordinate measuring apparatus and then the multilayerreflective film formed substrate formed with the fiducial mark andfiducial mark formation position information (specified fiducial markposition coordinates) in this case are correlated with each other andprovided to a user, the user can surely detect the fiducial mark in ashort time using this fiducial mark formation position information.Since the formation position of the fiducial mark is specified by thecoordinate measuring apparatus, conversion of reference coordinates ofan electron beam writing apparatus is enabled. Therefore, the userprovided with the multilayer reflective film formed substrate canaccurately collate defect positions easily specified based on thefiducial mark by a defect inspection apparatus and writing data witheach other so that it is possible to surely reduce defects in a finallymanufactured mask.

If defect information (position information, size, etc.) based on thefiducial mark is added to the above-mentioned fiducial mark formationposition information and provided to the user, the user can surelydetect the fiducial mark in a short time using this fiducial markformation position information and further can accurately correct(modify) writing data based on this defect information so as to reducethe influence due to defects, thereby reducing defects in a finallymanufactured mask.

If a reflective mask blank formed with an absorber film, which isadapted to absorb EUV light, on a multilayer reflective film of themultilayer reflective film formed substrate formed with the fiducialmark and fiducial mark formation position information are correlatedwith each other and provided to a user, the user can surely detect thefiducial mark in a short time using this fiducial mark formationposition information in the manufacture of a mask using this reflectivemask blank.

Also in the case of a mask blank in which a thin film to be a transferpattern is formed on a substrate, if the mask blank formed with afiducial mark at a predetermined position from the origin which was setbased on edge coordinates of the substrate and fiducial mark formationposition information in this case are correlated with each other andprovided to a user, or if, after the mask blank is formed with afiducial mark, a formation position of the fiducial mark is specified bya coordinate measuring apparatus and then the mask blank formed with thefiducial mark and fiducial mark formation position information in thiscase are correlated with each other and provided to a user, the user cansurely detect the fiducial mark in a short time using this fiducial markformation position information.

Also in the case of the mask blank, if defect information based on thefiducial mark is added to the fiducial mark formation positioninformation and provided to the user, the user can accurately correct(modify) writing data based on this defect information so as to reducethe influence due to defects, thereby reducing defects in a finallymanufactured mask.

[Multilayer Reflective Film Formed Substrate]

As shown in FIG. 7, this invention also provides a multilayer reflectivefilm formed substrate 30 in which a fiducial mark 13 of this inventionis formed on a multilayer reflective film 31 adapted to reflect EUVlight.

In FIG. 7, there is shown an example in which the fiducial mark 13 isformed by removing part of films constituting the multilayer reflectivefilm 31. Alternatively, the fiducial mark 13 may be formed by removingall layers constituting the multilayer reflective film 31.

The multilayer reflective film is a multilayer film in which lowrefractive index layers and high refractive index layers are alternatelylaminated. Generally, use is made of a multilayer film in which thinfilms of a heavy element or its compound and thin films of a lightelement or its compound are alternately laminated by about 40 to 60cycles.

For example, as a multilayer reflective film for EUV light having awavelength of 13 to 14 nm, use is preferably made of a Mo/Si cyclemultilayer film in which Mo films and Si films are alternately laminatedby about 40 cycles. Other than this, as a multilayer reflective film foruse in a region of EUV light, there is a Ru/Si cycle multilayer film, aMo/Be cycle multilayer film, a Mo compound/Si compound cycle multilayerfilm, a Si/Nb cycle multilayer film, a Si/Mo/Ru cycle multilayer film, aSi/Mo/Ru/Mo cycle multilayer film, a Si/Ru/Mo/Ru cycle multilayer film,or the like. The material may be properly selected according to anexposure wavelength.

For EUV exposure, in order to prevent distortion of a pattern due toheat in exposure, use is preferably made of, as a glass substrate 11, amaterial having a low thermal expansion coefficient in a range of0±1.0×10⁻⁷/° C., more preferably in a range of 0±0.3×10⁻⁷/° C. As thematerial having the low thermal expansion coefficient in this range, itis possible to use, for example, a SiO₂—TiO₂-based glass, amulticomponent glass-ceramic, or the like.

A main surface, on the side where a transfer pattern is to be formed, ofthe glass substrate 11 is surface-machined to have high flatness interms of ensuring at least pattern transfer accuracy and patternposition accuracy. For EUV exposure, the flatness is preferably 0.1 μmor less and particularly preferably 0.05 μm or less in a 142 mm×142 mmregion of the main surface, on the side where the transfer pattern is tobe formed, of the glass substrate 11. A main surface, on the sideopposite to the side where the transfer pattern is to be formed, of theglass substrate 11 is a surface which is electrostatically chucked whenit is set in an exposure apparatus. The flatness thereof is 1 μm orless, preferably 0.5 μm or less in a 142 mm×142 mm region.

As described above, the material having the low thermal expansioncoefficient, such as the SiO₂—TiO₂-based glass, is used as the glasssubstrate 11 of the multilayer reflective film formed substrate.However, with such a glass material, it is difficult to achieve highsmoothness such as a surface roughness of 0.1 nm or less in RMS byprecision polishing. Therefore, as shown in FIG. 7, it is preferable toform an underlayer 21 on the surface of the glass substrate 11 for thepurpose of reducing the surface roughness of the glass substrate 11 orreducing defects of the surface of the glass substrate 11. As a materialof such an underlayer 21, it does not need to have translucency forexposure light and it is preferable to select a material that can obtainhigh smoothness when a surface of the underlayer is precision-polishedand that is excellent in defect quality. For example, Si or a siliconcompound containing Si (e.g. SiO₂, SiON, or the like) is preferably usedbecause high smoothness is obtained when precision-polished and thedefect quality is excellent. Si is particularly preferable.

It is preferable that the surface of the underlayer 21 beprecision-polished to a smoothness which is required as a substrate fora mask blank. It is preferable that the surface of the underlayer 21 beprecision-polished to a root mean square roughness (RMS) of 0.15 nm orless, particularly preferably 0.1 nm or less. In consideration of theinfluence on a surface of the multilayer reflective film which is formedon the underlayer 21, it is preferable to precision-polish the surfaceof the underlayer 21 so that, in terms of the relationship with themaximum surface roughness (Rmax), Rmax/RMS becomes 2 to 10, particularlypreferably 2 to 8.

The thickness of the underlayer 21 is preferably in a range of, forexample, 75 nm to 300 nm.

[Mask Blank]

This invention also provides a reflective mask blank in which anabsorber film to be a transfer pattern is formed on the multilayerreflective film of the multilayer reflective film formed substratehaving the above-mentioned structure, and a mask blank in which a thinfilm to be a transfer pattern is formed on a mask blank glass substrate.

The multilayer reflective film formed substrate can be used as asubstrate for a reflective mask blank which is for manufacturing areflective mask, that is, which comprises, in order, on a substrate, amultilayer reflective film adapted to reflect exposure light (EUV light)and an absorber film for pattern formation adapted to absorb theexposure light (EUV light).

FIG. 8 shows a reflective mask blank 40 in which a protective layer(capping layer) 32 and an absorber film 41 for pattern formation adaptedto absorb EUV light are formed on the multilayer reflective film 31,formed with the fiducial mark 13, of the multilayer reflective filmformed substrate 30 of FIG. 7. On the side, opposite to the side wherethe multilayer reflective film and so on are formed, of the glasssubstrate 11, a back-side conductive film 42 is provided.

The absorber film 41 has the function of absorbing exposure light suchas EUV light and use is preferably made of, for example, tantalum (Ta)alone or a material composed mainly of Ta. As the material composedmainly of Ta, use is made of a material containing Ta and B, a materialcontaining Ta and N, a material containing Ta and B and furthercontaining at least one of O and N, a material containing Ta and Si, amaterial containing Ta, Si, and N, a material containing Ta and Ge, amaterial containing Ta, Ge, and N, or the like.

Normally, for the purpose of protecting the multilayer reflective filmin patterning the absorber film 41 or in pattern correction, theprotective film 32 or a buffer film is provided between the multilayerreflective film and the absorber film. As a material of the protectivefilm, use is made of silicon, ruthenium, or a ruthenium compoundcontaining ruthenium and one or more elements from niobium, zirconium,and rhodium. As a material of the buffer film, a chromium-based materialis mainly used.

As shown in FIG. 19, this invention also provides a reflective maskblank 45 in which a fiducial mark 13 of this invention is formed in anabsorber film 41 adapted to absorb EUV light. In FIG. 19, portionscorresponding to those in FIG. 8 are assigned the same symbols.

In FIG. 19, there is shown an example in which the fiducial mark 13 isformed by removing the absorber film 41 so that a protective film 32 isexposed. Alternatively, the fiducial mark 13 may be formed by removingthe absorber film 41 partially in depth, the fiducial mark 13 may beformed by removing the absorber film 41 and the protective film 32 sothat a multilayer reflective film 31 is exposed, or the fiducial mark 13may be formed by removing the absorber film 41, the protective film 32,and the multilayer reflective film 31 so that a substrate 11 is exposed.

FIG. 9 shows a binary mask blank 50 in which a light-shielding film 51is formed on a glass substrate 11. A fiducial mark 13 of this inventionis formed in the light-shielding film 51.

Although not illustrated, a phase shift mask blank is obtained byforming a phase shift film or a phase shift film and a light-shieldingfilm on a glass substrate 11. It may be configured such that theabove-mentioned underlayer 21 is provided on a surface of the glasssubstrate 11 if necessary.

The light-shielding film may be in the form of a single layer or aplurality of layers (e.g. a laminated structure of a light-shieldinglayer and an antireflection layer). When the light-shielding film hasthe laminated structure of the light-shielding layer and theantireflection layer, the light-shielding layer may have a structurecomprising a plurality of layers. Likewise, the phase shift film mayalso be in the form of a single layer or a plurality of layers.

As such a mask blank, there can be cited, for example, a binary maskblank having a light-shielding film made of a material containingchromium (Cr), a binary mask blank having a light-shielding film made ofa material containing a transition metal and silicon (Si), a binary maskblank having a light-shielding film made of a material containingtantalum (Ta), or a phase shift mask blank having a phase shift filmmade of a material containing silicon (Si) or a material containing atransition metal and silicon (Si).

As the material containing chromium (Cr), there can be cited chromiumalone or a chromium-based material (CrO, CrN, CrC, CrON, CrCN, CrOC,CrOCN, or the like).

As the material containing tantalum (Ta), there can be cited tantalumalone, a compound of tantalum and another metal element (e.g. Hf, Zr, orthe like), or a material containing tantalum and at least one elementfrom nitrogen, oxygen, carbon, and boron, such as, specifically, amaterial containing TaN, TaO, TaC, TaB, TaON, TaCN, TaBN, TaCO, TaBO,TaBC, TaCON, TaBON, TaBCN, or TaBCON.

As the material containing silicon (Si), there can be cited a materialcontaining silicon and at least one element from nitrogen, oxygen, andcarbon. Specifically, a material containing silicon nitride, siliconoxide, silicon carbide, silicon oxynitride, silicon carboxide, orsilicon carboxynitride is preferable.

As the material containing a transition metal and silicon (Si), therecan be cited, other than a material containing a transition metal andsilicon, a material containing a transition metal and silicon andfurther containing at least one element from nitrogen, oxygen, andcarbon. Specifically, a material containing a transition metal silicide,a transition metal silicide nitride, a transition metal silicide oxide,a transition metal silicide carbide, a transition metal silicideoxynitride, a transition metal silicide carboxide, or a transition metalsilicide carboxynitride is preferable. As the transition metal, use canbe made of molybdenum, tantalum, tungsten, titanium, chromium, hafnium,nickel, vanadium, zirconium, ruthenium, rhodium, niobium, or the like.Among them, molybdenum is particularly preferable.

[Mask]

This invention also provides a reflective mask in which the absorberfilm of the reflective mask blank having the above-mentioned structureis patterned, and a mask in which the thin film of the mask blank havingthe above-mentioned structure is patterned.

FIG. 10 shows a reflective mask 60 having an absorber film pattern 41 aobtained by patterning the absorber film 41 of the reflective mask blank40 of FIG. 8.

FIG. 11 shows a binary mask 70 having a light-shielding film pattern 51a obtained by patterning the light-shielding film 51 of the binary maskblank 50 of FIG. 9.

As a method of patterning the thin film such as the absorber film or thelight-shielding film, which is to be a transfer pattern, of the maskblank, the photolithography is the most suitable.

Although not illustrated, in the case of the phase shift mask blankhaving the phase shift film or the phase shift film and thelight-shielding film on the mask blank glass substrate, a phase shiftmask is obtained by patterning the thin film which is to be a transferpattern.

EXAMPLES

Hereinbelow, the embodiments of this invention will be described infurther detail with reference to Examples.

Example 1

A SiO₂—TiO₂-based glass substrate (size: about 152.4 mm×about 152.4 mm,thickness: about 6.35 mm) was prepared, wherein surfaces of thesubstrate were polished stepwise with cerium oxide abrasive particlesand colloidal silica abrasive particles using a double-side polishingmachine and then were surface-treated with low-concentrationfluorosilicic acid. The surface roughness of the obtained glasssubstrate was 0.25 nm in root mean square roughness (RMS) (measured byan atomic force microscope, measurement region: 1 μm×1 μm).

The surface shape (surface form, flatness) of both front and backsurfaces of the glass substrate was measured by a flatness measuringapparatus (UltraFlat manufactured by Tropel Corporation) (measurementregion: 148 mm×148 mm). As a result, the flatness of the front and backsurfaces of the glass substrate was about 290 nm.

Then, local surface machining was applied to the surfaces of the glasssubstrate, thereby adjusting the surface shape thereof.

The surface shape (surface form, flatness) and the surface roughness ofthe obtained glass substrate surfaces were measured. As a result, in a142 mm×142 mm measurement region, the flatness of the front and backsurfaces was 80 nm, i.e. 100 nm or less, and thus was satisfactory.

Then, using a B-doped Si target and using a mixed gas of Ar gas and Hegas as a sputtering gas, DC magnetron sputtering was carried out to forma Si underlayer of 100 nm. Then, stress reduction treatment was carriedout by applying thermal energy to the Si film.

Thereafter, in order to maintain the surface shape and to reduce thesurface roughness, a surface of the Si underlayer was precision-polishedusing a single-side polishing machine.

The surface shape (surface form, flatness) and the surface roughness ofthe obtained Si underlayer surface were measured. As a result, in a 142mm×142 mm measurement region, the flatness was 80 nm, i.e. 100 nm orless, and thus was satisfactory. Further, in a 1 μm×1 μm measurementregion, the surface roughness was 0.08 nm in root mean square roughnessRMS and thus was extremely excellent. Since the Si underlayer surfacehas an extremely high smoothness of 0.1 nm or less in RMS, backgroundnoise in a highly sensitive defect inspection apparatus is reduced,which is effective also in terms of suppressing false defect detection.

Further, in a 1 μm×1 μm measurement region, the maximum surfaceroughness (Rmax) was 0.60 nm and thus Rmax/RMS was 7.5. Accordingly,variation in surface roughness was satisfactorily small.

Then, using an ion-beam sputtering apparatus, given that a Si film(thickness: 4.2 nm) and a Mo film (thickness: 2.8 nm) formed one cycle,Si films and Mo films were laminated by 40 cycles to form a multilayerreflective film (total thickness: 280 nm) on the Si underlayer, therebyobtaining a multilayer reflective film formed substrate.

Then, fiducial marks having the following surface shape and concavecross-sectional shape were formed at predetermined portions of a surfaceof the multilayer reflective film. The fiducial marks were formed usinga focused ion beam. In this event, conditions were set to anaccelerating voltage of 50 kV and a beam current value of 20 pA.

In this Example, as each fiducial mark, a main mark and auxiliary markswere formed in the arrangement relationship shown in FIG. 2. The mainmark 13 a had a rectangular shape with a size of 5 μm×5 μm, wherein thedepth was set to about 280 nm because all layers constituting themultilayer reflective film were removed. The auxiliary marks 13 b and 13c each had a rectangular shape with a size of 1 μm×200 μm, wherein thedepth was set to about 280 nm because all layers constituting themultilayer reflective film were removed.

The cross-sectional shape of the fiducial mark was observed by an atomicforce microscope (AFM). As a result, as shown in FIG. 12, theinclination angle of a side wall was 85 degrees and the radius ofcurvature of a ridgeline portion between the surface of the multilayerreflective film and the side wall was about 250 nm, meaning that thecross-sectional shape was excellent.

It was confirmed by an electron beam writing apparatus or a mask blankinspection apparatus that the fiducial mark formed in the multilayerreflective film exhibited a contrast of as high as 0.025 and thus couldbe accurately detected and further that it could be detected with highreproducibility because variation in defect detection position was 83nm, i.e. 100 nm or less.

Then, the surface of the multilayer reflective film was subjected to adefect inspection using a mask blank defect inspection apparatus (Teron600 Series manufactured by KLA-Tencor Corporation). In this defectinspection, reference points were determined using the above-mentionedfiducial marks as references and convex and concave defect positioninformation based on relative positions to the determined referencepoints and defect size information were obtained, thereby producing adefect map. There was obtained the multilayer reflective film formedsubstrate with defect information (defect map) in which the multilayerreflective film formed substrate and these defect position informationand defect size information were correlated with each other. Thereflectance of the surface of the multilayer reflective film of thismultilayer reflective film formed substrate was evaluated by an EUVreflectometer. As a result, since variation in surface roughness of theunderlayer was suppressed, the reflectance was 67%±0.2%, which wassatisfactory.

Then, using a DC magnetron sputtering apparatus, a capping layer(thickness: 2.5 nm) made of RuNb and an absorber layer in the form of alaminate of a TaBN film (thickness: 56 nm) and a TaBO film (thickness:14 nm) were formed on the multilayer reflective film and, further, a CrNconductive film (thickness: 20 nm) was formed on the back side, therebyobtaining an EUV reflective mask blank.

Then, the obtained EUV reflective mask blank was subjected to a defectinspection using a mask blank defect inspection apparatus (Teron 600Series manufactured by KLA-Tencor Corporation). In the same manner asdescribed above, convex and concave defect position information usingthe above-mentioned fiducial marks as references and defect sizeinformation were obtained, thereby obtaining the EUV reflective maskblank with defect information in which the EUV reflective mask blank andthese defect position information and defect size information werecorrelated with each other.

Then, using this EUV reflective mask blank with defect information, anEUV reflective mask was manufactured.

First, a resist for electron beam writing was applied on the EUVreflective mask blank by spin coating and then baked, thereby forming aresist film.

Then, the defect information of the EUV reflective mask blank andpre-designed mask pattern data were collated with each other. Then, oneof the following corrections was made, i.e. correction to mask patterndata having no influence on pattern transfer using an exposureapparatus, correction to mask pattern data added with correction patterndata so as to, for example, hide a defect under a pattern when judged tohave an influence on the pattern transfer, and correction to maskpattern data capable of reducing the load of defect correction after themanufacture of a mask in the case of a defect not curable even bycorrection pattern data. Based on the corrected mask pattern data, amask pattern was written on the resist film by an electron beam and thendevelopment was carried out, thereby forming a resist pattern. In thisExample, since the relative positional relationship between the fiducialmarks and defects could be managed with high accuracy, it was possibleto accurately correct the mask pattern data.

Using the resist pattern as a mask, the TaBO film of the absorber layerwas etched with a fluorine-based gas (CF₄ gas) while the TaBN film ofthe absorber layer was etched with a chlorine-based gas (Cl₂ gas),thereby forming an absorber layer pattern on the capping layer.

Then, the resist pattern remaining on the absorber layer pattern wasremoved by hot sulfuric acid, thereby obtaining an EUV reflective mask.

The obtained EUV reflective mask was inspected using a mask defectinspection apparatus (Teron 600 Series manufactured by KLA-TencorCorporation). As a result, no convex defect was observed on themultilayer reflective film.

When the reflective mask thus obtained is set in an exposure apparatusto carry out pattern transfer onto a semiconductor substrate formed witha resist film, excellent pattern transfer can be carried out with nodefect of a transfer pattern due to the reflective mask.

Example 2

A reflective mask blank was manufactured in the same manner as inExample 1 except that fiducial marks in Example 1 were not formed in amultilayer reflective film, but formed in an absorber film.

The cross-sectional shape of the fiducial mark was observed by an atomicforce microscope (AFM). As a result, as in Example 1, the inclinationangle of a side wall was 87 degrees and the radius of curvature of aridgeline portion between a surface of the absorber film and the sidewall was about 120 nm, meaning that the cross-sectional shape wasexcellent.

It was confirmed by an electron beam writing apparatus or a mask blankdefect inspection apparatus that the fiducial mark formed in theabsorber film exhibited a contrast of as high as 0.020 and thus could beaccurately detected and further that it could be detected with highreproducibility because variation in defect detection position was 81nm.

In this Example, a surface of the multilayer reflective film of amultilayer reflective film formed substrate, in which the multilayerreflective film was formed on a substrate, was subjected to a defectinspection by a mask blank defect inspection apparatus (Teron 600 Seriesmanufactured by KLA-Tencor Corporation) using the center of a mainsurface of the substrate as a reference. Then, with respect to thereflective mask blank formed with the absorber film, convex and concavedefect position information using the fiducial marks as references anddefect size information were obtained using the same mask blank defectinspection apparatus as described above. Finally, collation was madebased on a plurality of defects which were consistent between defectinformation of the multilayer reflective film formed substrate anddefect information of the reflective mask blank, thereby obtaining theEUV reflective mask blank with defect information in which thereflective mask blank and these defect position information and defectsize information were correlated with each other.

In the same manner as in Example 1, an EUV reflective mask wasmanufactured. The obtained EUV reflective mask was inspected using amask defect inspection apparatus (Teron 600 Series manufactured byKLA-Tencor Corporation). As a result, no convex defect was observed onthe multilayer reflective film.

When the reflective mask thus obtained is set in an exposure apparatusto carry out pattern transfer onto a semiconductor substrate formed witha resist film, excellent pattern transfer can be carried out with nodefect of a transfer pattern due to the reflective mask.

Example 3

A synthetic quartz substrate (size: about 152.4 mm×about 152.4 mm,thickness: about 6.35 mm) was prepared, wherein surfaces of thesubstrate were polished stepwise with cerium oxide abrasive particlesand colloidal silica abrasive particles using a double-side polishingmachine and then were surface-treated with low-concentrationfluorosilicic acid. The surface roughness of the obtained glasssubstrate was 0.2 nm in root mean square roughness (RMS). The flatnessof the front and back surfaces of the glass substrate was about 290 nm.

Then, on the glass substrate, a light-shielding film in the form of alaminate of a TaN film and a TaO film was formed in the followingmanner.

Using a tantalum (Ta) target as a target, reactive sputtering (DCsputtering) was carried out by setting the power of a DC power supply to1.5 kW in a mixed gas atmosphere of xenon (Xe) and nitrogen (N₂) (gaspressure 0.076 Pa, gas flow rate ratio Xe:N₂=11 sccm:15 sccm), therebyforming a TaN film having a thickness of 44.9 nm. Subsequently, using aTa target, reactive sputtering (DC sputtering) was carried out bysetting the power of a DC power supply to 0.7 kW in a mixed gasatmosphere of argon (Ar) and oxygen (O₂) (gas pressure 0.3 Pa, gas flowrate ratio Ar:O₂=58 sccm:32.5 sccm), thereby forming a TaO film having athickness of 13 nm. In this manner, a light-shielding film for ArFexcimer laser (wavelength 193 nm) in the form of the laminate of the TaNfilm and the TaO film was formed, thereby manufacturing a binary maskblank. The light-shielding film had an optical density of 3.0 for ArFexcimer laser and a front-surface reflectance of 19.5%.

Then, fiducial marks which were the same as those in Example 1 wereformed at predetermined portions of a surface of the light-shieldingfilm. The fiducial marks were formed using a focused ion beam. In thisevent, conditions were set to an accelerating voltage of 50 kV and abeam current value of 20 pA.

The cross-sectional shape of the fiducial mark was observed by an atomicforce microscope (AFM). As a result, as in Example 1, the inclinationangle of a side wall was 83 degrees and the radius of curvature of aridgeline portion between the surface of the light-shielding film andthe side wall was about 300 nm, meaning that the cross-sectional shapewas excellent.

It was confirmed by an electron beam writing apparatus or a mask blankinspection apparatus that the fiducial mark formed in thelight-shielding film exhibited a contrast of as high as 0.02 and thuscould be accurately detected and further that it could be detected withhigh reproducibility because variation in defect detection position was80 nm.

The obtained binary mask blank was subjected to a defect inspectionusing a mask blank defect inspection apparatus (Teron 600 Seriesmanufactured by KLA-Tencor Corporation). Convex and concave defectposition information using the fiducial marks formed in thelight-shielding film as references and defect size information wereobtained, thereby obtaining the binary mask blank with defectinformation in which the binary mask blank and these defect positioninformation and defect size information were correlated with each other.

Then, using this binary mask blank with defect information, a binarymask was manufactured.

First, a resist for electron beam writing was applied on the binary maskblank by spin coating and then baked, thereby forming a resist film.

Then, as in Example 1, the defect information of the binary mask blankand pre-designed mask pattern data were collated with each other. Then,one of the following corrections was made, i.e. correction to maskpattern data having no influence on pattern transfer using an exposureapparatus, correction to mask pattern data added with correction patterndata when judged to have an influence on the pattern transfer, andcorrection to mask pattern data capable of reducing the load of defectcorrection after the manufacture of a mask in the case of a defect notcurable even by correction pattern data. Based on the corrected maskpattern data, a mask pattern was written on the resist film by anelectron beam and then development was carried out, thereby forming aresist pattern. Also in this Example, since the relative positionalrelationship between the fiducial marks and defects could be managedwith high accuracy, it was possible to accurately correct the maskpattern data.

Using the resist pattern as a mask, the TaO film was etched with afluorine-based gas (CF₄ gas) while the TaN film was etched with achlorine-based gas (Cl₂ gas), thereby forming a light-shielding filmpattern.

Then, the resist pattern remaining on the light-shielding film patternwas removed by hot sulfuric acid, thereby obtaining a binary mask.

The obtained binary mask was inspected using a mask defect inspectionapparatus (Teron 600 Series manufactured by KLA-Tencor Corporation). Asa result, no convex defect was observed on the glass substrate.

When the binary mask thus obtained was set in an exposure apparatus tocarry out pattern transfer onto a semiconductor substrate formed with aresist film, excellent pattern transfer was carried out with no defectof a transfer pattern.

Comparative Example

A multilayer reflective film formed substrate formed with fiducialmarks, a reflective mask blank, and a reflective mask were manufacturedin order in the same manner as in Example 1 except that the size of amain mark of each fiducial mark in Example 1 was set to 100 μm×100 μm.

The obtained EUV reflective mask was inspected using a mask defectinspection apparatus (Teron 600 Series manufactured by KLA-TencorCorporation). As a result, several tens of convex defects were observedon a multilayer reflective film.

As a result of examining the reason why several tens of convex defectswere observed on the multilayer reflective film, it was found out thatthe detection reproducibility of the fiducial marks formed in thisComparative Example was poor (particularly in a defect inspectionapparatus) so that mask pattern data could not be accuratelycorrected/modified based on defect information.

Example 4

Fiducial marks having a concave cross-sectional shape were formed atpredetermined portions of a surface of a multilayer reflective film of amultilayer reflective film formed substrate in Example 1. The fiducialmarks were formed using FIB (focused ion beam) as in Example 1. In thisevent, conditions were set to an accelerating voltage of 50 kV and abeam current value of 20 pA.

In this Example, edge coordinates of eight portions of four sides of thesubstrate were confirmed and then tilt correction was carried out to setthe origin at an arbitrary corner of the substrate. Then, the fiducialmark was formed by FIB at a predetermined position from the origin whichwas set on an edge basis as described above. Specifically, the fiducialmark was formed at a position distanced by 8000 μm, 8000 μm fromrespective edges of end faces both adjacent to the origin which was setat the arbitrary corner of the substrate on the edge basis. The fiducialmarks were formed in the same manner at four portions in total in thesubstrate plane.

As each fiducial mark, a main mark and auxiliary marks were formed inthe arrangement relationship shown at (a) in FIG. 16. The main mark 13 ahad a rectangular shape with a size of 5 μm×5 μm, wherein the depth wasset to about 280 nm because all layers constituting the multilayerreflective film were removed. The auxiliary marks 13 b and 13 c each hada rectangular shape with a size of 1 μm×120 μm, wherein the depth wasset to about 280 nm because all layers constituting the multilayerreflective film were removed.

It was confirmed by an electron beam writing apparatus or a mask blankinspection apparatus that the fiducial mark formed in the multilayerreflective film exhibited as high a contrast as that in Example 1 andcould be accurately detected in a short time using formation positioninformation of the fiducial mark (fiducial mark formation coordinates).

Further, it was possible to shorten the processing time of the fiducialmark by about 30 percent compared to Example 1.

Example 5

Fiducial marks were formed on a multilayer reflective film formedsubstrate in the same manner as in Example 3 except that each fiducialmark consisted of only a main mark having a rectangular shape with asize of 5 μm×5 μm.

It was confirmed by an electron beam writing apparatus or a mask blankinspection apparatus that the fiducial mark formed on the multilayerreflective film formed substrate exhibited as high a contrast as that inExample 1 and could be accurately detected in a short time usingformation position information of the fiducial mark (fiducial markformation coordinates).

Further, it was possible to shorten the processing time of the fiducialmark by about 60 percent compared to Example 1.

Example 6

As fiducial marks, only main marks each having a rectangular shape witha size of 5 μm×5 μm were formed at arbitrary positions. Specifically,the fiducial marks each having a concave cross-sectional shape wereformed at predetermined portions of a surface of a multilayer reflectivefilm of a multilayer reflective film formed substrate in Example 1. Thefiducial marks were formed using FIB (focused ion beam) as in Example 1.In this event, conditions were set to an accelerating voltage of 50 kVand a beam current value of 20 pA. Thereafter, center coordinates of thefiducial marks were measured by a highly accurate pattern positionmeasuring apparatus (LMS-IPRO4 manufactured by KLA-Tencor Corporation).As a result, it was confirmed that the fiducial marks were respectivelyformed at positions of (8022 μm, 8011 μm), (7999 μm, 144005 μm), (144004μm, 8017 μm), and (143982 μm, 144010 μm) with respect to the origin atan upper-left corner of the substrate.

It was confirmed by an electron beam writing apparatus or a mask blankinspection apparatus that the fiducial mark formed on the multilayerreflective film formed substrate exhibited as high a contrast as that inExample 1 and could be accurately detected in a short time usingformation position information of the fiducial mark (fiducial markformation coordinates).

In each of the above-mentioned Examples, the description has been givenof the example in which the fiducial mark was formed by a focused ionbeam, but not limited thereto. As also described before, the fiducialmark can be formed by photolithography, recess formation by laser lightor the like, machining trace by scanning a diamond stylus, indention bya micro-indenter, stamping by an imprint method, or the like.

In the above-mentioned Examples, the description has been given of theexample in which the underlayer was formed in each of the multilayerreflective film formed substrate and the reflective mask blank, but notlimited thereto. A multilayer reflective film formed substrate or areflective mask blank formed with no underlayer may also be used.

DESCRIPTION OF SYMBOLS

-   -   11 glass substrate    -   12 rough alignment mark    -   13 fiducial mark (fine mark)    -   13 a main mark    -   13 b, 13 c auxiliary mark    -   21 underlayer    -   30 multilayer reflective film formed substrate    -   31 multilayer reflective film    -   32 protective layer    -   40 reflective mask blank    -   41 absorber film    -   50 binary mask blank    -   51 light-shielding film    -   60 reflective mask    -   70 binary mask

The invention claimed is:
 1. A multilayer reflective film formedsubstrate, comprising: a substrate; a multilayer reflective film whichis formed on the substrate and which reflects EUV light; and a fiducialmark which serves as a reference for a defect position in defectinformation; wherein the fiducial mark comprises a main mark fordetermining a reference point for the defect position, and wherein themain mark has a point-symmetrical shape and has a portion with a widthof 200 nm or more and 10 μm or less with respect to a scanning directionof an electron beam or defect inspection light.
 2. The multilayerreflective film formed substrate according to claim 1, wherein the mainmark has a polygonal shape having at least two pairs of sides eachperpendicular to and parallel to scanning directions of the electronbeam or the defect inspection light.
 3. The multilayer reflective filmformed substrate according to claim 1, wherein the multilayer reflectivefilm is formed with the fiducial mark.
 4. A reflective mask blank,wherein an absorber film for absorbing the EUV light is formed on themultilayer reflective film of the multilayer reflective film formedsubstrate according to claim
 1. 5. A method of manufacturing themultilayer reflective film formed substrate according to claim 1,comprising: forming the fiducial mark at a predetermined position froman origin which was set based on edge coordinates of the substrate; andcorrelating the multilayer reflective film formed substrate comprisingthe fiducial mark and formation position information of the fiducialmark with each other.
 6. The multilayer reflective film formed substratemanufacturing method according to claim 5, further comprising: addingdefect information based on the fiducial mark to the formation positioninformation of the fiducial mark.
 7. A reflective mask blankmanufacturing method, comprising: correlating a reflective mask blankhaving an absorber film for absorbing EUV light on the multilayerreflective film of the multilayer reflective film formed substratecomprising the fiducial mark according claim 5 and the formationposition information of the fiducial mark with each other.
 8. A methodof manufacturing the multilayer reflective film formed substrateaccording to any of claim 1, comprising: specifying, after forming thefiducial mark, a formation position of the fiducial mark by a coordinatemeasuring apparatus; and correlating the multilayer reflective filmformed substrate comprising the fiducial mark and formation positioninformation of the fiducial mark with each other.
 9. A multilayerreflective film formed substrate, comprising: a substrate; a multilayerreflective film which is formed on the substrate and which reflects EUVlight; and a fiducial mark which serves as a reference for a defectposition in defect information; wherein the fiducial mark comprises amain mark for determining a reference point for the defect position andan auxiliary mark arranged around the main mark, and wherein the mainmark has a point-symmetrical shape and has a portion with a width of 200nm or more and 10 μm or less with respect to a scanning direction of anelectron beam or defect inspection light.
 10. The multilayer reflectivefilm formed substrate according to claim 9, wherein the auxiliary markhas a rectangular shape with long sides perpendicular to and short sidesparallel to the scanning direction of the electron beam or the defectinspection light.
 11. A reflective mask blank, comprising: a substrate;a multilayer reflective film which formed on the substrate and whichreflects EUV light; an absorber film which is formed on the multilayerreflective film and which absorbs the EUV light; and a fiducial markwhich serves as a reference for a defect position in defect information;wherein the fiducial mark comprises a main mark for determining areference point for the defect position, and wherein the main mark has apoint-symmetrical shape and has a portion with a width of 200 nm or moreand 10 μm or less with respect to a scanning direction of an electronbeam or defect inspection light.
 12. The reflective mask blank accordingto claim 11, wherein the absorber film is formed with the fiducial mark.13. The reflective mask blank according to claim 11, wherein thefiducial mark comprises the main mark and an auxiliary mark arrangedaround the main mark.
 14. The reflective mask blank according to claim13, wherein the auxiliary mark has a rectangular shape with long sidesperpendicular to and short sides parallel to the scanning direction ofthe electron beam or the defect inspection light.
 15. The reflectivemask blank according to claim 11, wherein the main mark has a polygonalshape having at least two pairs of sides each perpendicular to andparallel to scanning directions of the electron beam or the defectinspection light.
 16. A reflective mask, wherein the absorber film ofthe reflective mask blank according to claim 11 is patterned.
 17. Amethod of manufacturing the reflective mask blank according to claim 11,comprising: forming the fiducial mark at a predetermined position froman origin which was set based on edge coordinates of the substrate; andcorrelating the reflective mask blank comprising the fiducial mark andformation position information of the fiducial mark with each other. 18.A method of manufacturing the reflective mask blank according to claim11, comprising: specifying, after forming the fiducial mark, a formationposition of the fiducial mark by a coordinate measuring apparatus; andcorrelating the reflective mask blank comprising the fiducial mark andformation position information of the fiducial mark with each other. 19.A mask blank, comprising: a substrate; a thin film which is formed onthe substrate and which becomes a transfer pattern; and a fiducial markwhich serves as a reference for a defect position in defect information;wherein the fiducial mark comprises a main mark for determining areference point for the defect position, and wherein the main mark has apoint-symmetrical shape and has a portion with a width of 200 nm or moreand 10 μm or less with respect to a scanning direction of an electronbeam or defect inspection light.
 20. A mask, wherein the thin film ofthe mask blank according to claim 19 is patterned.
 21. A method ofmanufacturing the mask blank according to claim 19, comprising: formingthe fiducial mark at a predetermined position from an origin which wasset based on edge coordinates of the substrate; and correlating the maskblank comprising the fiducial mark and formation position information ofthe fiducial mark with each other.
 22. The mask blank manufacturingmethod according to claim 21, further comprising: adding defectinformation based on the fiducial mark to the formation positioninformation of the fiducial mark.
 23. A method of manufacturing the maskblank according to claim 19, comprising: specifying, after forming thefiducial mark, a formation position of the fiducial mark by a coordinatemeasuring apparatus; and correlating the mask blank comprising thefiducial mark and formation position information of the fiducial markwith each other.
 24. A mask blank, comprising: a substrate; a thin filmwhich is formed on the substrate and which becomes a transfer pattern;and a fiducial mark which serves as a reference for a defect position indefect information; wherein the fiducial mark comprises a main mark fordetermining a reference point for the defect position and an auxiliarymark arranged around the main mark, and wherein the main mark has apoint-symmetrical shape and has a portion with a width of 200 nm or moreand 10 μm or less with respect to a scanning direction of an electronbeam or defect inspection light.